L3 - Do you have the edge? Flashcards
How are discordant coastlines formed?
A discordant coastline occurs where bands of differing rock type run perpendicular to the coast.
Name a hard rock type this is resistant to erosion and creates a promontory and a softer rock type which is easily eroded creating a bay.?
Granite and the Clays of Bagshot Beds
What type of coastlines occur where beds, or layers, of differing rock types are folded into ridges that run parallel to the coast?
A concordant, longitudinal, or Pacific type coastline.
What type of coastlines occur where beds, or layers, of differing rock types are folded into ridges that run parallel to the coast?
A concordant, longitudinal, or Pacific type coastline.
What do the outer hard rock in coastlines (for example, granite) do ?
It’s provides a protective barrier to erosion of the softer rocks (for example, clays) further inland.
A cove is a circular area of water with a relatively narrow entrance from the sea. But how it formed?
Sometimes the outer hard rock is punctured, allowing the sea to erode the softer rocks behind. This creates a cove.
Name 4 stresses of a land slope (e.g. angle of slope)
- Rainwater / saturation
- Vibration, e.g. car
- Earthquakes
- Sea, cliff erosion
Name 3 stengths of a land slope (e.g. Lubricant layers)
- Tree / vegetation roots
- Consolidation of material
- Porosity of soil
Prolonged rainfall is a key factor that promotes landslides but what does it do
In prolonged rainfall the rainfall will saturate the soil and encourage soil movement.
Buildings is a key factor that promotes landslides but what does it do
Increases weight on the slope and adds to the downward pull of gravity
Removing vegetation is a key factor that promotes landslides but what does it do
Roots bind the soil together, vegetation uses up some of the moisture
Excavation is a key factor that promotes landslides but what does it do
Undercutting of slope increases instability
Permeability is a key factor that promotes landslides but what does it do
Water flows on surface of impermeable layer.
Rock type is a key factor that promotes landslides but what does it do
Weak saturated material or shattered rocks are more likely to move than solid bedrock
Bedrock is a key factor that promotes landslides but what does it do
Solid bedrock below weak materials, the junction forms the likely slide plane
What are the main causes of landslides in the UK
~Weathering
~Natural erosion -by sea or river
~Artificial erosion - by railways cuttings
~Ground subsidence and removal of support
~Deposition
~Seismic shocks / vibrations
~Human induced water regime change leading to surplus water lubricating soil
Rocks and Slopes
•Are not 1 uniform land mass •They will have hard and soft blocks of material, rock or soil etc. Which move relatively close to each other
•These blocks are separated by what?
These blocks are separated by joints, bedding planes or faults
Shear stress is related to cohesion and effective normal stress as shown by which equation
the Coulomb-Terzaghi equation
Mass movements occur when force exceeds resistance, give another way to name this
when stress > strength
Put factor of safety, shear strength and shear stress in a equation
Factor of safety = shear strength/ shear stress
How are cliffs shaped
Cliffs are shaped through a combination of erosion and weathering - the breakdown of rocks caused by weather conditions.
Give an example of soft rock which erodes easily to create gently sloping cliffs. Give an example of hard rock which is more resistant and erodes slowly to create steep cliffs.
Soft rock, eg sand and clay,
Hard rock, eg chalk,
Explain the process of cliff erosion
The process of cliff erosion
Weather weakens the top of the cliff.
The sea attacks the base of the cliff forming a wave-cut notch.
The notch increases in size causing the cliff to collapse.
The backwash carries the rubble towards the sea forming a wave-cut platform.
The process repeats and the cliff continues to retreat.
What are slope processes
Movement of material down slope under the force of gravity, often involving flowing water
Name the two main types on slope processes and how they work
–mass movements (downslope movement of slope material under influence of gravity only)
–water erosion (downslope movement of slope material under the influence of gravity and flowing water)
Name 5 types of mass movement (e.g. Rockfall)
Rock slide Block glide Toppling failure Debris slide Slump Debris flow
What is the rate of reaction in Holderness Coast
The average annual rate of erosion is around 2 metres per year. This is around 2 million tonnes of material every year.
What is the bedrock at Holderness Coast
Under lying the Holderness Coast is bedrock made up of Cretaceous Chalk. However, in most place this is covered by glacial till deposited over 18,000 years ago. It is this soft boulder clay that is being rapidly eroded.
